Zsa Zsa Weerts

Cost-effectiveness of peppermint oil in IBS 191 8 Introduction Irritable Bowel Syndrome (IBS) is a prevalent and chronic disorder of brain-gut- interaction characterized by chronic abdominal pain and altered bowel habits. 1 IBS has a large negative impact on quality of life (QoL) 2 and is associated with considerable costs for patients, healthcare systems and society. 3-5 Regarding direct costs to healthcare systems, IBS patients are reported to have increased numbers of consultations, emergency room visits, hospitalizations, and prescribed medications, when compared to patients without IBS. 2,6 Additionally, a large proportion of patients use over-the-counter (OTC) drugs or complementary medicine leading to high out of pocket costs. 6 Regarding indirect costs 3,4 , IBS patients are more likely to be both absent from work (absenteeism) and impaired during work (presenteeism) when compared to non-IBS patients. 6 Summed with the reduced QoL in patients, IBS leads to a high socioeconomic disease burden. 2,7,8 Effective therapies are therefore crucial to decrease this burden. Generally, symptom improvement should result in a better health-related QoL, less resource use and less productivity loss. Peppermint oil is a frequently used treatment for IBS and we previously reported the results of the largest randomized clinical trial (RCT) with peppermint oil to date. 9 A recent meta-analysis, including data from this trial, confirmed the therapeutic superiority of small-intestinal peppermint oil over placebo in IBS. 10 Trial based data on the cost-effectiveness of peppermint oil however, are lacking so far. The objective of this trial-based economic evaluation was therefore to assess the cost- effectiveness of peppermint oil compared with placebo, in patients with IBS. Materials and methods This economic evaluation was performed in a multicenter, placebo-controlled, double- blind RCT on the clinical efficacy of peppermint oil as a secondary outcome. The study was performed in four Dutch hospitals, one academic with a combined secondary/tertiary care function (Maastricht University Medical Center+, MUMC+), and three secondary care (Hospital Gelderse Vallei, Ede; Alrijne Hospital, Leiden; Medical Center Leeuwarden, Leeuwarden). The research protocol had been approved by the MUMC+ Committee of Ethics and has been registered in the US National Library of Medicine (Clinicaltrials.gov, NCT02716285). All study procedures were performed in compliance with GCP and the Declaration of Helsinki. All subjects had given a written